Fuse



W. J. HAWKINS.

FUSE.

AFPL|cAT|oN FILED FEB.25.1920.

1,41 8,7 l O. Patented J une 6, 1922.

2 SHEETS-SHEET l.

6 J wvwws W. J. HAWKINS.

FUSE.

APPLICATION FILED FEB. 25, 1920.

1,418,710. PatellvdJuIl@ 6, 1922.

2 SHEETS-SHEET 2.

UNITED STATES 'WILFORD J'. HAWKINS, OF MONTCLAIR, NEW JERSEY.

FUSE.

Specification of Letters Patent.

Patented June 6,1922.

Application le'd February 25, 1920. Serial No. 361,317.

To all whom t rmay concern Be it known that I, WILFORD J. IIAwK1Ns, a citizen of the United States, residing at Montclair,.in the county of Essex; State of New Jersey, have invented certain new and useful Improvements in Fuses; and I' do hereby declare the following to ybe a full, clear, and exact description ofV the invention, such as will enable others skilled in the artv to which it appertains to make and use the same.

This invention relates to electric fuses and is directed to the provision of a fuse of an improved construction which is effective in opening an electric circuit when overload conditions exist without a loud report and Without danger of settingfre to objects near the fuse. One of the features of the conf` struction constituting the present invention; involves the provision of a mufiier for suppressing the noise and flames incident to the rupture of a fuse link. To this end the link is enclosed within an inner tube of insulating material Which in turn is enclosed within an outer tube; each of these tubes has passages throu h it spaced apart lengthwise of the fuse and the sizes of the tubes are such that a narrow space Iis provided between them. Thus the exit from the fuse link is a long narrow and tortuous one, well adapted for suppressing the noise and fiame incident to the burning out of a fuse.

Another feature of the invention resides in the construction whereby the parts of the fuse as a whole are gripped together. To this end the inner tube is provided with washers at its ends and the endsy of the fuse link are bent along the surfaces of these washers; the inner unit consisting of the washers and the fusible link is of slightly greater length than the outer tube` and constitutes a strut such that when end caps are screwed up on the threaded ends of 'the outer tube, this strut is gripped between them and all of the parts are held rigidly together.

Another feature of the invention involves the provision of Washers of heavy `paper upon the fusible link at the ends of the inner tube in close contact with the sides of the fuse whereby flame and hot gases de-- veloped by the fuse when it burns out are prevented from coming in contact with the ends of the fusible link where they are gripped by the associated metal parts for in that event there might be` danger of the ends of a burned out link becoming welded to other parts. u f

Another. feature of the invention involves the provision of a reinforcement for a tube of fibre or other similar material employed as a casing for a fuse. I have found that the. tubes of fibre commonly employed as casings for a fuse do not possess the requisite degree of strength to withstand radial pressure developed by the blowing of a fuse and I therefore propose to reinforce such ,a tube by applylng to it a suitable -metallic wrapping in the .form of a spiral winding of w1re or a wrapping of woven wire fabric or the l1k e, care being observed to prevent this metallic reinforcement from coming into electrical contact with the ends of the fuse. Such a metallic reinforcement is desirable in any form of fuse having a casing of insulatlng material for strengthening it to withstand radial pressure but it is of especial value 1n a fuse of the construction vabove descrlbed consisting of inner and outer tubes of lnsulating material with a narrow space between them forming a muffler.

In the drawings, Fig. l is a central longitudinal section of the fuse; Fig. 2 is a similar view on a plane at right angles to the f plane ofthe section of Fig. l as indicated by the line 2-2 of Fig. 1; Fig. 3 is an end View of the fuse; Fig. 4 is a transverse section on line 4 4 of Fig. 2; Fig. 5 is a transverse section on line 5-5 of Fig. 2; Fig. 6 is a view similar to Fig. l illustrating a slight modification of the construction; Fig. 7 is a .transverse section on line 7-7 of Fig. l; F1g. 8 is a view corresponding to Fig. l illustrating a further modification.; Fig. 9 is a transverse section on line 9-9 of F1g. 8; Fig. 10 is a View correspondin to Fig. and lllustrating a further modication and Flg. 11 is a transverse section on line 11-11 of Fi 10.

Re erring to these drawings, 8 indicates a tube of insulating material, preferably fibre. This tube is threaded at its ends for coaction with the end caps 9 which are interlorly threaded as shown. -One of these end caps is closed at its end and the other has an opening therethrou h as shown4 at 10 so that a mark on the en of the fuse link may be seen through this opening 10.

Within the tube 8 is a second tube l1 of 1 insulating material, preferably fibre. Its exterlor diameter approximates the interior -diameter of theftube 8 though it is not the saine as the interior diameter of tube 8, thus providing a narrow space between t-hese two tubes. The inner tube 11 is provided with a plurality of transverse passages therej through as shown at 12, the several passages being spaced apart from each other, and the outer tube 8 1s also provided with transverse holes or passages 13 spaced from each other and from the openings in the tube 11. This assemblage of the two tubes forms a muffler such that the exit from the fuse link is through the central openingin the tube 11, then through the staggered holes 12 near the ends of the inner tube 11, then through the narrow space between the tubes 11 and 8 and then out through the holes 13 in the tube 8 which are located near the center of the length of the fuse. A tortuous passage of substantial length is thus provided, a portion of which is of very small width and this constitutes a muilier formuffiing the sound incident to rupture of the fuse link and suppressing pressures developed as a result of rupture of the link. I

The fuse link is shown at 14. 1t consists preferably of a flat strip which is reduced in width near the center as shown in Fig. 2. The ends of this fuse link pass through washers of thick paper, as card board, as is indicated at 15. One or more such washers may be provided at each end of tube 1 1. Each of these Washers is a disc corresponding in diameter to the exterior diameter of the tube 11 and is provided with a central cut corresponding in length to the width of the fuse 14. The material of the washer is not cut away but is merely slit and when the fuse link is passed through this slit the material adjacent to the slit is bent slightly as is indicated in the drawings, but it hugs the fuse link 14 closely. The primary function of these washers is to prevent the escape of ame or hot gasesq along the fuse link into contact with the devices which grip the ends of the fuse linkv for in that case the lends of the link might become welded to those devices. TWashers of heavy paper serve this function very well, particularly when they are slit for the passage of the fuse-link without having any of the material of the washer cut away.

Beyond the paper washers 15 are washers 16 of metal, preferably brass, which are of the size of the inner tube 11 and are provided with central slots through which the ends of the fuse-link 14 pass. At the end of the fuse which is rovided with the closed end cap, the end of the fuse link 14 is bent up as shown at 17 and this bent end lies against the face of the washer 16. 1When tightening up the end caps, the end 17 of the fuse-link is gripped between the washer 16 and the end wall of the end cap. 9. At the opposite end of the fuse, the link is bent along the face of the washer 16 and is then bent back upon itself as shown at 18. This end 18 may have numbers stamped thereon indicating the rating of the fuse-link as indicated in Figs. 3 and 4 and this rating may be read through the opening 10 in the end cap 9.

The inner unit consisting of the tube 11, washers 15, washers 16 and link 14 with its ends bent along the surfaces of the washers 16 is of slightly greater length than the outer tube S. Thus, when the end caps 9 are screwed upon the outer tube 8,the ends of the inner unit are gripped between the ends of the end caps 9, thus subjecting all of the parts of the inner unit to longitudinal pressure and holding them in the proper relation.

1n Figs. 6 and 7 a slight change in the construction above described is made. The metallic washer at oneI end of the fuse has no central slot therethrough for the passage of the 'fuse-link. Instead, this washer 19 has a slot out therein at the periphery as shown at 2O in Fig. 7. The fuse-link 21 instead of passing through the end washer is bent laterally after passing through the paper washers 15 as is shown at 22. At the periphery of the washer 19 the fuse-link passes through the slot 2O and then up along the outer face of the washer 19 as shown at 23. ln other respects the construction shown in Figs. 6 and 7 is like that shown in the preceding figures. This construction of Figs. 6 and 7 is preferred in fuses of relatively large electrical capacity. ln such fuses, on account of the greater thickness of the fusible-link, it is undesir able to make a sharp bend in the links such as is shown in Fig. 1, whereas the bend shown in Fig. 7 from the inner face to the outer face of the disc 19 is one which may be made without danger of breakage of the fuse-link.

1t will be noted that the construction above described is one which includes a casing for a fuse-link consisting of inner and outer tubular members, a narrow space between those members and openings or passages through each of the two members, the several passages being spaced apart lengthwise of the fuse. The structure thus constitutes a muliler for suppressing the noise and flame incident to rupture of the fuse-link and the muiliing effect is the more pronounced by reason of the tortuous passage from the interior to the exterior of the casing. 1t will be noted also that the inner member consisting of the inner tube and the washers at the ends of that tube constitute a strut by which the fuse-link is bound or pinched to hold it rigidly and this assembling of the parts is eifected by merely screwing up the end caps upon the outer tube. This is a hand operation so that the work of substituting a new fuse-link for the remains of one that was burned out may bev accomplished without resort toeven such tools as a screw driver.

The paper washers at the ends of the inner tube hug the walls of the fuse-link so closely as to effectually guard against the spread of hot gases or flame through them to the metallic washers lying beyond them; this guards effectually against heating the metallic washers and the ends vof the fuse; link lying against them to such extent as might result in welding ofthe ends of a ruptured fuse-link to the washers. Furthermore, the danger of an operator placing two links in a fuse to increase its carrying capacity is eliminated asthe slots in the nietallic washers 16 may be accurately sized to correspond with the width of the fuselinks to be employed with them so that they can receive but one link at a time. If the rating of this link be stamped uponits end, this rating may be read through the opening in' the end cap as above referred to.'

Figs.v 8 to 11 inclusive illustrate the construction employed in Fig. 6 with the addition of a means for reinforcin the tubular casing to better enable it to wit stand radial pressure as heretofore described. In Fig. 8 the inner tube 11 is shown as provided with a reinforcement 30 consisting of a spiral winding of wire .encircling the tube 11 Apractically from end to end. The ends 31 of this winding 30 are secured to the tube 11 in any suitable manner, as for instance by bending the ends of the wire radially inward and inserting them in holes in the tube 11, as for instance the holes 12 or smaller holes specificall rovided for the reception of the'ends o t e wire. Such a winding as that illustrated in Figs. 8 and 9 affords the necessary reinforcement for the tube 11 to withstand the radial pressure incident to the blowing of a fuse, and furthermore, this winding may be emplfyed in such a manner as to increase the mu ing effect. Thus, the diameter of the wire 30 may be practically the same as the width of the spa-ce between the inner and outer tubes so that gases passing from the interior to the exterior of the fuse are forced to take a more or less spiral path in fiowing from the openings 12 through the inner tube at the ends thereof to the openings 13 in the outer tubel at about the middle thereof. It will be understood, however, that when the winding of wire is employed for the sole purpose of'afl'ording the necessary reinforcement against radial pressure it may be applied to the exterior of the outer tube 8 if desired instead of to the inner tube 11. In any case, however, the construction must be such as to admit of no possibility of electrical connection of the ends of the fuse by the reinforcing wire. If the wire is applied to the outer tube 8 its ends must be adequatel spaced from the end caps 9, and if it is app led to the inner tube 11-1ts ends must be adequately spaced from the washers 19 or other metallic parts employed for gri in the ends of the fuse-link. v Pp g Figs. 10 and 11 illustrate a construction corresponding closel to that of Figs.- 8 and tubes it will assist in mufliing the gases ldeveloped by the burnin out of a fuse. As above noted, care mustltbeexercised to eliminate the possibility of electrical connection of the ends of the fuse by Vthis wrapping.

In all of the constructions above described it will be noted that the gripping together of the elements of the fuse is effected by tightening the metallic end caps which are threaded upon non-metallic members, that is, upon the threaded ends'of the tube of fibre. This construction, that is, a construction which avoids the use of a metalto-metal contact, is very desirable. When a metal-to-metal contact of the gripping elements is employed, it frequently happens kthat the threads become so fouled by the products of combustion as to cause them to bind, making it difficult or even impossible to open the fuse casing for the purpose of substituting a new link for one which-has been burned out. This objectionable characteristic of fuses having this metal-to.-

metal contact is eliminated or at least is greatly reduced in a construction wherein the gripping elements are one metallic and the other non-metallic. Furthermore, in a muffler construction of the character herein illustrated and described, wherein the gases developed by the burnin out of a fuse are conducted over a prescri edy path from the interior to the exterior of the fuse body, the products of combustion are kept away from the threaded connection of the end caps to the fuse body and the danger of fouling the threads is correspondingly reduced.

I claim: l

1. A fuse comprising the combination of an outer tube, an inner tube therein whose exterior diameter is less than the interior diameter of the outer tube so that a space is provided between the two tubes, said tubes having openings therethrough which vare spaced apart lengthwise of the fuse washers of heavy paper engaging the ends of the inner tube, a fusible link passing through the inner tube and paper washers and end caps on the outer tube to which the ends of the link are electrically connected.

2. A fuse comprising the combination of an outer tube and an inner tube therein, the two tubes beingvspaced apart and having openings through their walls which are spaced apart lengthwise of the fuse, paper Washers engaging the ends of the inner tube., a fusible link passing through the inner tube and paper washers and end caps threaded upon the ends of the youter tube and adapted, when screwed up, to grip the ends of the fusible link between them and the ends of the inner tube.

3. A fuse comprising the combination oft' inner and outer tubes'of insulating material spaced apart and provided with openings which are spaced lengthwise of the fuse, slotted paper washers upon the ends o'f the inner tube approximating in diameter the exterior diameter of the inner tube, a fusible link passing through the inner tube and through the slots in said washers and having its ends bent to extend along the faces of the washers, and end caps threaded upon the ends of the outer tube and adapted, when screwed up, to grip the bent ends of the Jfusible link between the ends of the end caps and the said washers.

4. A fuse comprising the combination of inner and outer tubes, washers of heavy paper upon the ends of the inner tubes hav` ing slots therethrough, a fusible link extending through the inner tube and the slots in the' washers, metallic washers engaging the ends of the fusible link and end caps on the outer tube adapted to grip the inner tube, washers and link between them.

5. A fuse comprising the combination of enema and coacting with the'threads upon the ends s of the outer tube whereby tightening up of the end caps causes the end walls of those caps to grip the inner tube, the washers and the ends of the fusible link between them and hold those parts rigidly.

6. In a "fuse, the combination of a tubular casing of insulating material consisting or inner and outer tubes having outlets there in, a fusible link passing through the casing and a reinforcement spirally arranged between the tubes and forming therewith a passageway between said outlets.

7. In a "fuse, the combination of inner and outer tubes of insulating material spaced apart and having openings therethrough which are spaced lengthwise of the fuse, a fusible link passing through the inner tube and a spiral winding of wire between the tubes and forming therewith a passageway between said openings.

ln testimony whereof I aiiix my signature.

WlLFORD J. HATWKINS. 

